Those involved in the alleged rigging of Britain's wholesale gas market will face the "full force of the law", Energy Secretary Ed Davey has warned.

Mr Davey promised "firm action" if there was any truth in allegations of gas price manipulation made by a whistleblower to the Financial Services Authority (FSA) and energy watchdog Ofgem.

In a statement to MPs, Mr Davey said: "I see it as my job to protect consumers, not least the most vulnerable who can suffer the most when markets are abused."

He said it was not possible to understand what impact any attempted manipulation, if proven, had on the market or prices paid by consumers. But the Government had "absolute determination to clamp down on any abuse that is uncovered, wherever and by whoever".

Prime Minister David Cameron's official spokesman said that if the claims, published in the Guardian, were true then regulators should come down "very hard" on those responsible. He added that energy price manipulation was "totally unacceptable".

All six of the big energy companies have released statements denying any involvement in attempts to fix the £300 billion market. The industry trade body, Energy UK, which represents the companies, said its members would co-operate fully with the regulators.

The FSA and Ofgem are both looking into allegations made by whistleblower Seth Freedman, who worked at ICIS Heren, a company responsible for setting so-called benchmark prices. Mr Freedman raised the alarm after identifying what he believed to be attempts to distort the prices reported by the company.

Ofgem was warned by ICIS Heren that it had seen evidence of suspect trading on September 28, the date that marks the end of the gas financial year. It is believed prices went down by about 0.4% on September 28 - a key date as it can have an influence on future prices, according to the Guardian.

In a statement to MPs, Mr Davey said: "These allegations of market manipulation are being taken very seriously. We will support the regulators taking whatever steps necessary to ensure that the full force of the law is applied, if they are true, so that any guilty parties are held to account."

Speaking during a visit to Italy, Mr Cameron said: "The allegation on gas pricing is extremely serious. I'm absolutely determined we get a good deal for British customers."